Harold Corwin

NGC 3979 = IC 2976. Here is a galaxy discovered twice by Lewis Swift, once toward the beginning of his systematic sweeping for new nebulae (April 1886), and once toward the end (May 1897). His first position is not too bad, being only 8 seconds of time and 1.2 arcmin off the galaxy.

But he was not the first to see it; that was Edward Holden in April of 1881. Holden found it first on the 23rd, but only estimated the RA then. On the 27th, he measured it at 42 seconds of time preceding the star BD -1d 2593. And that position is close to the modern one. But for the NGC entry, Dreyer chose to use an average, at least in RA, of Holden's and Swift's; he adopted Holden's declination (about 1.5 arcmin north of the galaxy).

For the IC, of course, Dreyer had only Swift's second position, 1.5 minutes off -- no wonder he thought Swift had found a new nebula! But there is nothing in Swift's position. The identification is ensured by Swift's comment about the "vF * near nf". This is the same star that Holden called "A star 11.5 n and f 30 [arcsec]."

― NGC Notes by Harold Corwin

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